The present invention relates to a storage system for managing data used by a computer. More specifically, the present invention is directed to a storage system for managing data through a wide area network, and a method for holding/managing files of the data.
Very recently, since information technology has advantageously progressed, amounts of data which are produced in enterprises are considerably increased. For instance, since data are formed in individual divisions/departments of a firm, managements of these formed data are necessarily carried out in these respective divisions/departments within this firm. As one example of data managements executed in enterprises, backup operations of formed data are carried out. In a backup operation, for example, important information (data) on business activities which have been stored in a magnetic disk apparatus are copied, or duplicated on a secondary storage apparatus such as a tape storage device from the magnetic disk apparatus. Frequency degrees of executions of such backup operations are considerably increased while amounts of data are increased.
Since such data managements are carried out in an intensive manner, data can be managed in a centralizing manner, so that cost required for managing data in enterprises can be reduced. As one example, while data are distributed to individual divisions/departments in a firm, backup operations of these distributed data are carried out every day in the respective divisions/departments. In contrast to this example, when information (data) is centralized so as to be managed in an intensive manner, a higher efficiency may be achieved as to data management aspects.
High reliable large-scale storage subsystems typically known as a RAID (redundant arrays of inexpensive disk) have been marketed as apparatus suitable for centralizing information. In such a RAID, since a storage area having a capacity of several tera-bytes is subdivided into a plurality of small logical storage regions, information as to each of small groups can be combined with each other to form one information group in an intensive manner. While such a feature owned by RAID is utilized, data which have been distributed/managed in individual divisions/departments of an enterprise could be managed in an centralizing manner in a large-scaled computer center and the like installed in an information processing department of this enterprise.
A trend of the above-described data centralizing management is extended over data centralizing managements of enterprises. Currently, service providers are coming out in a market, while these service providers manage data owned by a plurality of enterprises in a data center in an outsourcing manner. In such a data center, the following aspect is necessarily required. That is, data owned by a plurality of enterprises must be managed in safety and quick manners. Therefore, such a means capable of more easily managing information is required in a data center. However, while a storage area is employed as a block unit, data are handled in a RAID, so that a manager of such a data center can hardly manage these data.
On the other hand, a file server called as a “network attached storage” (abbreviated as an “NAS”) has been proposed as an apparatus capable of referring to data from a plurality of hosts, while difficulties of the data managements in the unit of block may be compensated. In this NAS, such an access operation can be carried out by employing such a network protocol as to the NFS (network file system) and the CIFS (common internet file system), while a personal computer (PC) and a workstation (WS) are equipped with these NFS and CIFS. As a result, data managements can be carried out in the unit of file, so that the data can be managed in a easier manner, as compared with the data management executed in the unit of block.